How Much Sleep Do You Really Need?

November 08, 2008

How much sleep do you really need? Probably a lot less than you think, says one expert. It's well known that a good night's sleep is essential for health. But oversleeping has been linked to a host of medical problems, including:

Diabetes: In a study of almost 9,000 Americans, researchers found a relationship between sleep and the risk of diabetes. People who slept more than nine hours each night had a 50 percent greater risk of diabetes than people who slept seven hours per night. This increased risk was also seen in people who slept less than five hours per night.

Obesity: Sleeping too much could make you weigh too much, as well. One recent study showed that people who slept for nine or 10 hours every night were 21 percent more likely to become obese over a six-year period.

Headaches: Sleeping longer than usual can cause head pain. Researchers believe this is due to the effect oversleeping has on certain neurotransmitters in the brain, including serotonin. People who sleep too much during the day and disrupt their nighttime sleep may also find themselves suffering from headaches in the morning.

Back pain: There was a time when doctors told people suffering from back pain to head straight to bed. But those days are long gone -- they now recommend against sleeping more than usual, when possible.

Depression: Roughly 15 percent of people with depression sleep too much. This may in turn make their depression worse, because regular sleep habits are important to the recovery process. In fact, in certain instances, sleep deprivation can be an effective treatment for depression.

Heart disease: A careful analysis of the data from the Nurses' Health Study, which involved nearly 72,000 women, showed that women who slept nine to 11 hours per night were 38 percent more likely to have coronary heart disease.

Death: Multiple studies have found that people who sleep nine or more hours a night have significantly higher death rates. No specific reason for this correlation has been determined.

Meanwhile, the common assertion that you need eight or more hours of sleep each night may be incorrect. According to some experts, most people need less than eight hours of sleep each night. Several large studies over the past 40 years show that the average healthy adult sleeps for seven to seven-and-a-half hours a night, and that should be plenty from a physical perspective. Some adults need even less than that and can function normally on just five hours of sleep a night.
It’s no mystery that if you go too long without sleep, your mind will not function properly. Sleep deprivation can actually cause changes in your brain activity similar to those experienced by people with psychiatric disorders.

But just how much sleep do people need? Is sleeping five or six hours a night enough, or do you need more like eight or nine?

Generally, it’s recommended that you get at least eight hours of sleep a night. But this is based on the notion that our ancestors slept around nine hours each night, and therefore we should too. But according to Professor Jim Horne of the Sleep Research Centre, this is a myth.

In reality, this misguided belief was based on a 1913 study that found children aged 8 to 17 slept for nine hours a night. Adults may have slept less. So according to Horne, it’s perfectly possible for some adults to thrive on five, six or seven hours of sleep a night.

However, sleep researchers have also found that it takes just a single night of sleeping only four to six hours to impact your ability to think clearly the next day. The research is really all over the place.

Another study in Diabetes Care found that sleeping five hours or less, or nine hours or more each night may increase your risk of developing diabetes. Another study found that those who slept about seven hours had the highest survival rate, and those who slept less than 4.5 hours had the worst. Nine hours of sleep or more each night was also associated with a higher mortality risk, however.

So how much sleep should you strive for each night?

There is No “Magic” Number

Your age and activity level will determine your sleep needs to some extent. Children and teens, for instance, need more sleep than adults. However, your sleep needs are individual to you. You may require more or less sleep than someone of the same age, gender and activity level.

• Basal Sleep Need: The amount of sleep you need an a regular basis for optimal performance

• Sleep Debt: The accumulated sleep lost due to poor sleep habits, sickness, environmental factors and other causes

Studies suggest that healthy adults have a basal sleep need of seven to eight hours each night. However, if you haven’t been sleeping well and have accumulated a sleep debt, you may still feel tired even if you’ve slept a full seven or eight hours one night. If you have a sleep debt, you may be especially tired at the times when your circadian rhythm naturally dips -- such as overnight or in the mid-afternoon.

If you have accumulated a sleep debt, you can “pay it off” by getting more sleep for a few nights, and then should return to your basal sleep need.

Getting Just the Right Amount of Sleep

There is well proven evidence that sleeping too little will have devastating effects on your health, including increasing your risk of diabetes, heart problems, obesity, depression, substance abuse and car accidents.

The role of too much sleep, on the other hand, is still being investigated. Research suggests that too much sleep increases your risk of death, yet low socioeconomic status and depression are also significantly associated with long sleep. So it could be that other factors are contributing to the health risks of too much sleep, and it is not the sleep itself that is the problem.

Still other researchers have suggested that your body will not let you sleep more than you need to, while others say sleeping less may actually be healthy if you have a tendency to oversleep.

For now it seems the wisest choice is to stay somewhere in the middle. As the graph from NSF below shows, staying somewhere in the middle ranges of seven to eight hours of sleep a night appears to be best. As always, you should let your body be your guide, sleeping more if you feel tired, and sleeping less if you feel you’ve overslept.

How Long Are Most Americans Sleeping?

The average time spent in bed is 6 hours and 55 minutes -- with 6 hours and 40 minutes spent actually sleeping, according to NSF’s 2008 Sleep in America poll. NSF recommends getting at least 7 to 9 hours of sleep each night, but you should always tailor that to your individual needs.

If you’re looking for a quick guide, the following chart from NSF has some general guidelines for all the members of your family:

If you or another family member is having trouble sleeping -- whether you are not able to fall asleep, wake up too often, don't feel well-rested when you wake up in the morning, or simply want to improve the quality and quantity of your sleep -- I’ve compiled a list of 33 tips you can use to get a good night’s sleep. I highly recommend reading this list, printing it out, and keeping it somewhere handy to reference until your sleep needs are being met.

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